Internally finned tube



M 7, 1942. s K A ERSEN 2,289,163

INTERNALLY FINNED TUBE Filed June '7, 1948 Patented July 7, 1942INTERNALLY FINNED TUBE Sol-en K. Andersen, Racine, Wis., assignor toYoung Radiator Company, Racine, Wls., a corporation of Wisconsin IApplication June 7, 1940, Serial No. 339,258

2 Claims.

The present invention relates to heat transfer devices and particularlythe type used for cooling the lubricating oil of an internal combustionengine with either the jacket fluid or a blast of air, the oil beingforced through the tubes and the jacket fluid forced around the outsideof the tubes. When a blast of air is used as the cooling medium, thetubes are provided with closely spaced fins in order to increase theheat transfer capacity of the device.

One of the greatest improvements made in the past in heat transferdevices when heating a blast of air or wherein a blast of air is usedfor the cooling medium was in the supplying of the tubes with closelyspaced fins through which the tubes extend. My invention applies thesame principle to the insideoi the tubes so as to greatly increase theefiiciency of the device and greatly reduce its size and cost.

In recent years it has been the custom to cool the lubricating oil ininternal combustion engines. In some devices for this purpose, an airblast is forced between the finsand tubes for cooling. In other devicesof the class, the tubes are surrounded by the jacket fluid as a coolingmedium. In stationary internal combustion engines, cold water isfrequently used as a cooling medium.

The heat transfer capacity of a finned bundle of tubes or of a bundle oftubes surrounded by water is very good but the heat transfer capacity ofoil passing through the tubes is very low as compared to the capacityfor transferring the heat to the water or to the air.

My invention relates to means for increasing the heat transfer capacityfrom the oil to the tube somewhat similar to the method used forincreasing the heat transfer capacity from the tube to a blast of air bymeans of closely spaced fins.

An object of the present invention is to approach or practically balancethe heat transfer capacity between the oil and tube with the heattransfer capacity from the tubes to the water or air.

I accomplish the foregoing results by supplying the tubes with internalfins, the fins, however, being placed longitudinally in the tube so asto parallel the flow of oil just as fins are positioned on the outsideof the tubes so as to parallel the fiow of air.

I have devised my internal fins whereby they may be bonded to the insidewalls of the tubes. Therefore it is thought I have provided the laststep in heat transfer devices particularly when used for cooling thelubricating oil or for that matter, when used for cooling or heating anyfluid passed through the tubes.

.To these and other useful ends, my invention consists of parts,combinations of parts, or their equivalents, and method of manufacture.as hereinafter set forth and claimed and shown in the accompanyingdrawing inwhich:

Fig. 1 is a side view of one type of heat transfer device making use ofclosely spaced fins which are bonded to the exterior of the tubes, thetubes being of the flattened type and equipped with my invention, thebottom header being sectioned so as to illustrate the manner of securingthe tubes to the header plate.

Fig. 2 is a fractional rear view of the device illustrated in Figure 1.

Fig. 3 is a section through one of the tubes taken on line 3-3 of Figure2.

Fig. 4 is a transverse sectional view of a round tube equipped with oneform of my invention.

It will be understood that the design illustrated in Figures 1, 2 and 3is adapted for oil cooling where the pressure of the oil is low. Thedesign shown in Figure 4 is adapted for oil cooling when the pressure ofthe oil is high.

In Figures 1 and 2, the headers are of a type quite different fromheaders adapted for high pressure. In these figures, the upper header inits entirety is designated by reference character A and the lower headeris designated in its entirety by reference character B.

Header A is provided with an inlet or outlet opening l0. Header B isprovided with a similar opening as at H, the latter opening beingindicated by dotted lines. The tube plates of headers A and B areadapted to receive the ends of tubes H as illustrated in Figure 1.

Tubes 12 are provided with a multiplicity of closely spaced fins l3,these fins are preferably provided with flanges (not shown) which arebonded to the tubes in the usual manner and the ends of the tubes arebonded to the tube plates in the usual manner.

I provide a longitudinally zig zag shaped internal fin which in itsentirety is designated by reference character C. The edges of member Care preferably turned outwardly as at l5. Before member C is placed inthe tube, edges C5 are considerable further apart than the internaltransverse length of the tube. The external width of member C is aboutthe same as the internal width of the tube. Thus it will be seen thatwhen member C is forced into the tube, the folds of member C will beforced together and the fins.

When assembling external fins to tubes, the

custom is to supply a suitable amount of acid to the exterior of thetube so when the bonding material is molten, it will be fused to the finflanges. In placing the internal fins in the tubes, I pursue this samemethod. That is, the interior of the tube is tinned and when the heat isapplied for bonding the tube to the outside fins, the inside fins willalso be fuse bonded to the tubes. The same process is followed when noexternal fins are provided.

It will be understood that either the internal fins or the inside of thetube or both may be tinned before the fins are positioned in the tube orany other method may be used for applying the bonding material.

In the design shown in Figure 3, clearly there are eleven points thatwill be bonded to the tubes. In Figure 4 I illustrate another form oftubes and internal fins wherein the fins in their en- 1 tirety aredesignated by reference character D and are somewhat similar to member Cand adapted to be forced into a round tube 2|. These round tubes may besupplied with exterior fins as in Figure 1 but whether furnished withexternal fins or not, the inside walls of the tubes and fin contactpoints may be bonded as already described.

Member D is designed so the apexes 22 and the ends 23 of this member aretightly held against the wallof the tubes. Thus, as illustrated. thefins will be bonded to the tube at seven different points.

In any design the internal fins add many times to the metal contact withthe oil.

Material from which members C and D are formed is quite thin thereforethe internal area of the tube is not reduced to a material extent but aswill be noted, the metal contact with the oil will be multiplied manytimes.

It will be seen that I have provided a simple means for increasing thesurface contact of the oil which means, as will be noted, may bedesigned so as to increase the metal to oil contact over 500%. In fact,my device practically eliminates the major disadvantages mentioned inthe present preamble.

Clearly the headers and tube assembly bear no part of the presentinvention. Figures 1 and 2 are used merely to illustrate one applicationof the present invention.

Having thus shown and described my invention, I claim:

1. A device of the class described, comprising a tube havinglongitudinally positioned internal fins, said fins comprising a singlestrip folded a number of times longitudinally accordion-like and adaptedto form yielding pressure contact between its edges, all of the apexesand the wall of the tube.

2. A device of the class described, comprising a tube havinglongitudinally positioned internal fins, said fins comprising a singlestrip folded a number of times longitudinally accordion-like and adaptedto form yielding pressure contact between its edges, all of the apexesand the wall of the tube and being bonded thereto.

SOREN K. ANDERSEN.

